Human tissue is structured mainly of self-assembled polymers (proteins) and ceramics (bone minerals), with metals present as trace elements with molecular scale functions. However, metals and their alloys have played a predominant role as structural biomaterials in reconstructive surgery, especially orthopedics, with more recent uses in non-osseous tissues, such as blood vessels. With the successful routine use of a large variety of metal implants clinically, issues associated with long-term maintenance of implant integrity have also emerged. This review focuses on metallic implant biomaterials, identifying and discussing critical issues in their clinical applications, including the systemic toxicity of released metal ions due to corrosion, fatigue failure of structural components due to repeated loading, and wearing of joint replacements due to movement. This is followed by detailed reviews on specific metallic biomaterials made from stainless steels, alloys of cobalt, titanium and magnesium, as well as shape memory alloys of nickel–titanium, silver, tantalum and zirconium. For each, the properties that affect biocompatibility and mechanical integrity (especially corrosion fatigue) are discussed in detail. Finally, the most critical challenges for metallic implant biomaterials are summarized, with emphasis on the most promising approaches and strategies.

Metallic implant biomaterials

In vitro and in vivo corrosion measurements of magnesium alloys.

Bioceramics of calcium orthophosphates

Zero-dimensional, one-dimensional, two-dimensional and three-dimensional nanostructured materials for advanced electrochemical energy devices

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications.

Development of 2D SnO2/rGO Nano-Composites for H2S Gas Sensor Using Electrochemical Impedance Spectroscopy at Room Temperature

In the last few years corrosion of equipment in the paper industry has become a universal problem. The currently used 316L SS (UNS S31603) is no longer sufficiently resistant to corrosion. An investigation was undertaken to study the pitting behavior and the nature and composition of passive films formed on high-Cr-Ni-Mo alloys in a simulated white water environment. Cyclic polarization studies and x-ray photoelectron spectroscopy (XPS) were deployed to understand the nature of passive films formed. The formation of a stable protective oxide film on the surface of Alloy 59 enhanced the corrosion resistance of the alloy. The major alloying elements Cr, Ni, and Mo were enriched on the surface, thereby preventing the breakdown of the passive film and provoking passivation of the alloy. XPS analysis of the passive film for Alloy 59 indicated the presence of chromium hydroxide (Cr[OH]3) and chromate (Cr2O3) as major constituents in the outermost and sputtered surface, respectively. The formation of st...

Surface Characterization and Pitting Behavior of High-Cr-Ni-Mo Alloys in Simulated White Water Environment

Development of an electrochemical biosensor for determination of dopamine by gold modified poly(thiophene-3-boronic acid)-polyphenol oxidase modified electrode

Surface modified ZnO nanomaterial is widely used in the field of bioimaging worldwide due to its optical properties, electronic characteristics and biocompatibility. Fluorescent enhanced, Polyquaternium-7(PQ7) capped, ZnO hexagonal nano disks (ZnO-PQ7) were synthesised by simple wet chemical method. The structural and optical properties of ZnO-PQ7 hexagonal nano disks were characterized using XRD, UV-Visible, Fluorescence, HRTEM, EDAX and FTIR studies. The size of synthesised ZnO-PQ7 were around 30-45 nm as confirmed by HRTEM studies. Fluorescence emission intensity increased with increase in PQ7 concentration. ZnO-PQ7 was further conjugated with folic acid (FA) to target human breast cancer cell line (MCF-7) via EDC/NHS coupling chemistry. Conjugation of folic acid with ZnO-PQ7 was confirmed by FTIR studies. The cell viability study using Methyl thiazolyltetrazolium(MTT) assay has demonstrated that the ZnO-PQ7 conjugated FA composites (ZnO-PQ7-FA) exhibit low toxicity towards MCF-7 up to a concentration of 125 μg/mL. Confocal laser scanning microscopic images confirmed the uptake of ZnO-PQ7-FA nanoparticles by MCF-7 cells. This study reveals ZnO-PQ7-FA nano disks as a potential imaging agent for detection of cancer cells. The synthesis route reported in this article is simple and easy to follow for the synthesis of ZnO-PQ7-FA in bulk quantities with high purity.

Synthesis of Hexagonal ZnO-PQ7 Nano Disks Conjugated with Folic Acid to Image MCF - 7 Cancer Cells.

Electrophoretic deposition (EPD) was employed to coat TiO2 and TiO2+CeO2 on AISI type 304L stainless steel (SS) to improve its corrosion resistance. Coatings were obtained by following three main steps, namely formation of a suspension of the charged TiO2 particles with addition of CeO2, deposition of the suspended particles on the electrode under the influence of a dc electric field, and sintering of the particulate deposit at 1073 K for 2 h in vacuum to form a dense and continuous film. The uniform deposits of TiO2 and TiO2+CeO2 formed on the surface shown good sintering characteristics and were characterised using X-ray diffraction (XRD) technique. The electrochemical investigation of the coatings in neutral chloride media was carried out to obtain open circuit potential (OCP) and potentiodynamic anodic polarisation behaviour in order to evaluate their corrosion resistance. The electrochemical parameters shifted towards noble direction for the TiO2 and CeO2+TiO2 coated specimens in comparison ...

T. M. Sridhar

Papers

Development of 2D SnO2/rGO Nano-Composites for H2S Gas Sensor Using Electrochemical Impedance Spectroscopy at Room Temperature

Surface Characterization and Pitting Behavior of High-Cr-Ni-Mo Alloys in Simulated White Water Environment

Development of an electrochemical biosensor for determination of dopamine by gold modified poly(thiophene-3-boronic acid)-polyphenol oxidase modified electrode

Synthesis of Hexagonal ZnO-PQ7 Nano Disks Conjugated with Folic Acid to Image MCF - 7 Cancer Cells.

Electrophoretic deposition of TiO2 and TiO2 + CeO2 coatings on type 304L stainless steel